The invention relates to a drinking vessel, for example a vessel such as a children's drinking vessel and preferably an infant drinking vessel.
A range of infant cups are known, for example of the type generally termed trainer cups, including a cup-like body often including handles for ease of use by a infant, a cover and a drinking spout provided on the cover. The cup is easier to handle and allows the infant to drink from the cup with less risk of spillage.
Various improvements to infant cups are known. In one example a trainer cup includes a slit valve membrane fixed at the tip of a rigid spout, which allows liquid to flow when the infant sucks but closes otherwise. As a result the cup is largely spill-proof under normal conditions.
Problems exist with the known arrangement, however. The moulding and fitting of the membranes may be a complex and costly operation, residue may be trapped where the membrane and spout meet, and because of the typically small orifice at the spout and the fragility of the membrane it may be difficult to clean. In addition, the child is often required to suck very hard to open slit valve membranes of this type which can be tiring and offputting for the child. Because the slit valves are very fragile they can be easily damaged, a particular risk in view of the use of the cup by a child, and the likelihood that a child will be left unattended with it because of its spillproof nature.
In addition, individual components within the system cannot be varied, as a result of which it is necessary to purchase a new product if any component fails or if the infant needs to move onto a new stage—for example if a stiffer valve action is required.
Yet further, as liquid is removed from the known cups, a negative pressure may develop in the cup which may make further drinking yet harder and removal of the lid equally difficult. It is difficult to open the valve manually to overcome this problem without damaging it.
A particular problem with valves of the known type arises when fruit juices are drunk from the vessel—in this case the fibres can clog the slit and prevent it from sealing properly, which can give rise to leakage.
Yet a further problem arises with arrangements such as this because of the rigid spout. In some instances biting or sucking on a hard spout can lead to tooth damage for the infant during the important teething stage, especially for infants up to 9 months of age. As the known systems allow liquid to flow only under pure suction, “grazing” is encouraged whereby the infant sucks continually, as can be the case with more standard feeding bottles. This can lead to the infant's teeth being bathed for long periods in the liquid in the cup, which will often be a sweet drink, and again can give rise to tooth damage.
Various other valved designs are known for infant drinking cups. For example PCT/GB00/00479, commonly assigned herewith, relates to an arrangement in which a flexible spout having an orifice cooperates with a pin or plug closing the orifice in an unflexed state such that when the spout is stretched away from the pin liquid can flow. It is desired to improve yet further the long term performance of such an assembly and further enhance the seal between the parts taking into account creep of materials with age whilst not prejudicing ease of drinking.
According to another known system described in GB 2 333 770 an infant cup includes a valve at the base of the mouthpiece including a flexible annular diaphragm valve member. When suction is applied the inner diameter of the diaphragm flexes away from a seat allowing fluid flow. As a negative pressure builds up in the vessel the outer diameter of the diaphragm flexes away from a “breather hole” to allow air in and equalise the pressure in the vessel.
Problems with systems with small parts include difficulty in cleaning and the possibility of a choking hazard for infants.
Other known arrangements include U.S. Pat. No. 5,186,347 and WO 99/47029, which suffer from problems of the type identified above.